1. Field of the Invention
The present invention relates to a seating apparatus used on the chair and to the chair with the said seating apparatus structure.
2. Description of Related Art
The sitting plane of the chair is usually situated parallel to horizontal plane as shown in FIG. 35. FIG. 35 is the schematic diagram of the chair with the person who sits on it. Though the sitting plane of the relaxing use chair is slanted to the backward lower and the chair back is declined backward to be able to sit lying on his back, the office chair used in front of the office desk has the horizontal sitting base plate in order to look at the documents straight.
As the sitting base plate of the chair is situated almost parallel to the horizontal plane, the angle between the spine 1 and the thigh 2 of the sitting person is smaller than about 100 degrees and almost near to 90 degrees in usual case as seen in FIG. 35.
When we sit long hours in this position, it comes the stress around the waist and comes at last the lower back pain. Concerning about an example way to avoid such kinds of the back pain, the posture improving ways to insert the seating pad or cushion under the hips in order to enlarge the angle between the spine and the thigh can be seen in U.S. Pat. Nos. 6,413,194 and 5,402,545, in which the section shape of the cushion is tapered forward in order to enlarge the angle between the spine and the thigh over 90 degrees. The method to insert the spacers of wedge shape section is presented in Japanese Patent Application Publication Laid-Open No. 2000-79135. The example of the spacer with springs is presented in Japanese Patent Application Publication Laid-Open No. 1999-244099.
On the other hand, a sit knee chair is known as the one which enables the person to sit with the angle from about 110 to 135 degrees between his or her spine and thigh, and which is composed of the seating plane tilted forward about 10 to 30 degrees and the knee supporting plane tilted in the reverse direction against the seating plane. An example of sit knee chair can be seen in U.S. Pat. No. 4,589,699 and has the feature that several tens of percent of sitting person's body weight fall on the knee supporting plane, and the sitting person's body is prevented to slip down the seating plane and given a steady sitting situation. Another example of sit knee chair is called as balans chair by STOKKE Company or HAG Company and could be seen in Internet URL:http://www.malsyo.co.jp/balans.html on Nov. 5, 2003.
The other type of chair for curing or preventing the lower back pain, in which the sitting plane is tilted or moved automatically, are presented in Japanese Patent of No. 3,106,360 and No.2,524,462.
[Patent Document 1]                U.S. Pat. No. 6,413,194        
[Patent Document 2]                U.S. Pat. No. 5,402,545,        
[Patent Document 3]                U.S. Pat. No. 4,589,699        
[Patent Document 4]                Japanese Patent Application Publication Laid-Open No. 2000-79135.        
[Patent Document 5]                Japanese Patent Application Publication Laid-Open No. 1999-244099        
[Patent Document 6]                Japanese Patent of No. 3,106,360        
[Patent Document 7]                Japanese Patent of No.2,524,462.        